<h2>DESCRIPTION</h2>

<em>t.rast.to.rast3</em> is designed to convert a space time raster
dataset (STRDS) into a space time voxel cube. A space time voxel cube
is a 3 dimensional raster map layer (3D raster map or voxel map layer)
that as time as unit for the z-dimension.
<p>
A space time raster dataset that should be converted into a space time
voxel cube must have a valid temporal topology. Hence, overlapping or
inclusion of time stamps is not allowed. The granularity of the STRDS
is used to set the resolution of the 3D raster map layer and to sample
the registered time stamped raster map layers.
<p>
Gaps between raster map layer in the STRDS will
be represented by NULL values in the voxel map layer.


<h2>NOTES</h2>

The reference time for all space time voxel cubes is
1900-01-0100:00:00. This allows the alignment space time voxel cubes
with different granularities.
<p>
Be aware that the granularity of a STRDS is used to sample time stamped
map layers! If you have gaps between monthly intervals that have the
size of a second, the monthly intervals will be sampled by a second
based granularity as well. This may result in millions of space time
voxel cube layers!

<h3>Management of open file limits</h3>
The maximum number of raster maps that can be processed is given by the 
per-user limit of the operating system. For example, both the the hard and soft
limit for users is typically 1024. The soft limit can be changed with e.g. 
ulimit -n 4096 (UNIX-based operating systems) but not higher than the 
hard limit. If the latter is too low, you can as superuser add an entry in

<div class="code"><pre>
/etc/security/limits.conf
# &lt;domain&gt;      &lt;type&gt;  &lt;item&gt;         &lt;value&gt;
your_username  hard    nofile          4096
</pre></div>

This will raise the hard limit to 4096 files. Also have a look at the overall 
limit of the operating system
<div class="code"><pre>
cat /proc/sys/fs/file-max
</pre></div>
which, on modern Linux systems, is several 100,000 files.


<h2>EXAMPLE</h2>
To create a voxel map layer from a subset of the <em>tempmean_monthly</em>
space time dataset, run:

<div class="code"><pre>
# create the subset for 2012 data
t.rast.extract input=tempmean_monthly output=tempmean_monthly_later_2012 \
               where="start_time >= '2012-01-01'"

# set the right 3D region
g.region -p3 res3=500

# convert to 3D raster map
t.rast.to.rast3 input=tempmean_monthly_later_2012@climate_2009_2012 output=tempmean_monthly_2012

t.info type=raster_3d input=tempmean_monthly_2012
 +-------------------- 3D Raster Dataset -------------------------------------+
 |                                                                            |
 +-------------------- Basic information -------------------------------------+
 | Id: ........................ tempmean_monthly_2012@climate_2009_2012
 | Name: ...................... tempmean_monthly_2012
 | Mapset: .................... climate_2009_2012
 | Creator: ................... lucadelu
 | Temporal type: ............. absolute
 | Creation time: ............. 2014-11-28 11:10:51.679294
 +-------------------- Absolute time -----------------------------------------+
 | Start time:................. 2012-01-01 00:00:00
 | End time:................... 2013-01-01 00:00:00
 +-------------------- Spatial extent ----------------------------------------+
 | North:...................... 320000.0
 | South:...................... 10000.0
 | East:.. .................... 935000.0
 | West:....................... 120000.0
 | Top:........................ 1357.0
 | Bottom:..................... 1345.0
 +-------------------- Metadata information ----------------------------------+
 | Datatype:................... DCELL
 | Number of columns:.......... 620
 | Number of rows:............. 1630
 | Number of cells:............ 12127200
 | North-South resolution:..... 500.0
 | East-west resolution:....... 500.0
 | Minimum value:.............. -0.534994
 | Maximum value:.............. 28.794653
 | Number of depths:........... 12
 | Top-Bottom resolution:...... 1.0
 | Registered datasets ........
 +----------------------------------------------------------------------------+


r3.info tempmean_monthly_2012
 +----------------------------------------------------------------------------+
 | Layer:    tempmean_monthly_2012          Date: Fri Nov 28 11:10:50 2014    |
 | Mapset:   climate_2009_2012              Login of Creator: lucadelu        |
 | Location: nc_spm_temporal_workshop                                         |
 | DataBase: /grassdata                                                       |
 | Title:    Space time voxel cube                                            |
 | Units:    none                                                             |
 | Vertical unit: months                                                      |
 | Timestamp: none                                                            |
 |----------------------------------------------------------------------------|
 |                                                                            |
 |   Type of Map:  3d cell              Number of Categories: 0               |
 |   Data Type:    DCELL                                                      |
 |   Rows:         620                                                        |
 |   Columns:      1630                                                       |
 |   Depths:       12                                                         |
 |   Total Cells:  12127200                                                   |
 |   Total size:           28414287 Bytes                                     |
 |   Number of tiles:      4230                                               |
 |   Mean tile size:       6717 Bytes                                         |
 |   Tile size in memory:  23520 Bytes                                        |
 |   Number of tiles in x, y and  z:   47, 45, 2                              |
 |   Dimension of a tile in x, y, z:   35, 14, 6                              |
 |                                                                            |
 |        Projection: Lambert Conformal Conic (zone 0)                        |
 |            N:     320000    S:      10000   Res:   500                     |
 |            E:     935000    W:     120000   Res:   500                     |
 |            T:       1357    B:       1345   Res:     1                     |
 |   Range of data:   min = -0.53499434 max = 28.79465315                     |
 |                                                                            |
 |   Data Source:                                                             |
 |                                                                            |
 |                                                                            |
 |                                                                            |
 |   Data Description:                                                        |
 |    This space time voxel cube was created with t.rast.to.rast3             |
 |                                                                            |
 |   Comments:                                                                |
 |    r.to.rast3 input="2012_01_tempmean@climate_2009_2012,2012_02_tempmea\   |
 |    n@climate_2009_2012,2012_03_tempmean@climate_2009_2012,2012_04_tempm\   |
 |    ean@climate_2009_2012,2012_05_tempmean@climate_2009_2012,2012_06_tem\   |
 |    pmean@climate_2009_2012,2012_07_tempmean@climate_2009_2012,2012_08_t\   |
 |    empmean@climate_2009_2012,2012_09_tempmean@climate_2009_2012,2012_10\   |
 |    _tempmean@climate_2009_2012,2012_11_tempmean@climate_2009_2012,2012_\   |
 |    12_tempmean@climate_2009_2012" output="tempmean_monthly_2012" tilesi\   |
 |    ze=32                                                                   |
 |                                                                            |
 +----------------------------------------------------------------------------+
</pre></div>

<h2>SEE ALSO</h2>

<em>
<a href="r3.mapcalc.html">r3.mapcalc</a>,
<a href="r3.info.html">r3.info</a>
</em>

<h2>AUTHOR</h2>

S&ouml;ren Gebbert, Th&uuml;nen Institute of Climate-Smart Agriculture

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